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Hemolytic disease of the newborn
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<p>Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an <a href="/facts/Alloimmunity/y9U62TnH">alloimmune</a> condition that develops in a <a href="/facts/Fetus/evocHd0Y">fetus</a> at or around birth, when the <a href="/facts/Immunoglobulin_G/cKzc83tk">IgG</a> molecules (one of the five main types of <a href="/facts/Antibody/MX8pdTdP">antibodies</a>) produced by the mother pass through the <a href="/facts/Placenta/7XUoks1b">placenta</a>. Among these antibodies are some which attack <a href="/facts/Antigen/9JlAernG">antigens</a> on the <a href="/facts/Red_blood_cell/Kggpq8Jh">red blood cells</a> in the <a href="/facts/Fetal_circulation/20hbvEzS">fetal circulation</a>, <a href="/facts/Hemolysis/1WpVYHkP">breaking down and destroying the cells</a>. The fetus can develop <a href="/facts/Reticulocytosis/5eg6Q1np">reticulocytosis</a> and <a href="/facts/Anemia/AgEPPmg8">anemia</a>. The intensity of this fetal disease ranges from mild to very severe, and fetal death from heart failure (<a href="/facts/Hydrops_fetalis/gmhmgq9s">hydrops fetalis</a>) can occur. When the disease is moderate or severe, many <a href="/facts/Erythroblast/bwcLuW7j">erythroblasts</a> (immature red blood cells) are present in the fetal blood, earning these forms of the disease the name <i>erythroblastosis fetalis</i> (<a href="/facts/British_English_language/ymJR5Rnd">British English</a>: <i>erythroblastosis foetalis</i> </p><p>HDFN represents a breach of <a href="/facts/Immune_privilege/9AU4tN4U">immune privilege</a> for the fetus or some other form of impairment of the <a href="/facts/Immune_tolerance_in_pregnancy/eIhCErwk">immune tolerance in pregnancy</a>. Various types of HDFN are classified by which alloantigen provokes the response. The types include <a href="/facts/Hemolytic_disease_of_the_newborn_(ABO)/Ga7jmmTF">ABO</a>, <a href="/facts/Rh_disease/nYcHWXrG">anti-RhD</a>, <a href="/facts/Hemolytic_disease_of_the_newborn_(anti-RhE)/ffKBR4rE">anti-RhE</a>, <a href="/facts/Hemolytic_disease_of_the_newborn_(anti-Rhc)/RjLQaxkg">anti-Rhc</a>, anti-Rhe, anti-RhC, multiantigen combinations, and <a href="/facts/Hemolytic_disease_of_the_newborn_(anti-Kell)/IKHu6eLV">anti-Kell</a>. Although global prevalence studies of the differential contribution of those types are lacking, regional <a href="/facts/Population_studies/uoFwl7Uq">population studies</a> have shown the anti-RhD type to be the most common cause of HDFN, followed by anti-RhE, anti-RhC, and anti-Rhc. </p>